Heat treating apparatus and method of assembly therefor



May 11, 1965 F. M. FAHRENWALD 3,182,810

HEAT TREATING APPARATUS AND METHOD OF ASSEMBLY THEREFOR Filed June 29, 1962 I NVENTOR.

WW/M" ffzr/er 1% fame 5" United States Patent 3,182,810 HEAT TREATING APPARATUS AND METHQD OF ASSEMBLY THEREFOR Francis M. Fahrenwald, Chicago, Ill., assignor to The Fahralloy Company, a corporation of Illinois Filed June 29, 1962, Ser. No. 206,379 13 Claims. (Cl. 211118) This invention relates in general to apparatus for suspending workpieces for travel through a treatment zone, and more particularly to a suspending assembly for supporting relatively heavy parts, such as automobile crankshafts, from a conveyor in a heat treating furnace.

Mass production quantities of many parts, such as automobile crankshafts, must be heat-treated to impart the necessary physical properties to the parts. One well known method of treating a large number of parts is to suspend them from a traveling conveyor which moves through a furnace, the length of the furnace and the rate of travel of the conveyor being so related that the necessary heat treatment is performed during the time the parts are in transit through the furnace.

One conventional suspension assembly for suspending automobile crankshafts from a conveyor passing through a furnace comprises essentially a hook member which is either made integral with, or at least connected to, a strap assembly or cage. The cage consists of a generally horseshoe shaped ring from which a bail extends perpendicularly upwardly, the point of connection of the bail to the ring being approximately at the midpoint of the two generally parallel arms of the ring. The hook in turn is connected to the top of the bail. A plurality, usually four, buttons project upwardly from the U-shaped ring to provide support points upon which rests the workpiece to be heat-treated. The clearance between the bail and ring is sufiicient to allow the workpiece to be slid into the cage and then placed downwardly upon the buttons.

Generally, these assemblies are made from material which is non-uniform in cross-section in order to obtain the necessary physical properties. Furthermore, diiferent shaped parts which are integral with one another lie in different planes. As a result failure of the parts invariably occurs due to cracking of the parts at the junctions between cross-sections of difierent shapes. The cracking results from the large internal stresses which are created primarily by the repeated heating and cooling to which the parts are subjected.

Accordingly, one of the primary objects of my invention is to provide a suspension assembly for carrying objects such as automobile crankshafts through heat treatment zones, such as heat treating furnaces, which is simple to make, inexpensive, and less subject to failure due to repeating heating and cooling than existing suspension assemblies, 7

Another object is to provide a suspension assembly for heat treating furnaces in which like parts are of approximately uniform cross-section throughout, and in which no two parts of materially differing cross-section are integrally, or mechanically connected to one another, but, rather, are simply loosely hooked together whereby expansion and contraction of each part can occur without any effect on adjacent parts.

Yet another object is to provide a suspension assembly for conveying objects, such as automobile crankshafts, through heat treating zones which has a low initial cost and whose life is longer than existing suspension assemblies.

Yet a further object is to provide a suspension assembly which may be easily assembled and disassembled, and, when once assembled, loosely, but mechanically, locked in place.

Yet a further object is a method for providing a 3- point support for conveying articles through a zone of high heat which is unaffected by dimensional changes in the components of the suspension assembly due to difference in temperatures to which the assembly is exposed.

Other objects and advantages will become apparent upon a reading of the following description of the in- Vention.

The invention is illustrated more or less diagrammatically in the accompanying drawings, wherein:

FIGURE 1 is a perspective View of my suspension assembly hanging from a support base, in this instance a spider connected by means not shown to a conveyor;

FIGURE 2 is a side view of my suspension assembly;

FIGURE 3 is a front view of my suspension assembly with the spacer member omitted for clarity;

FIGURE 4 is a cross-section taken substantially along the line 44 of FIGURE 3; and

FIGURE 5 is a top plan view of the spacer.

Like reference numerals will be used to refer to like parts throughout the following description of the drawings.

My suspension assembly is indicated generally at in FIGURE 1. It is shown as supported from a base or carrying structure 11. The carrying structure, in this instance, comprises a downwardly extending stem 12 from which four quadrant arms 13, 14, 15 and 16 extend, the stem and quadrant arms forming a spider. A collar 17 is located at the end of each quadrant arm, and a flange 18 is spaced inwardly along the arm a distance suificient to accommodate my suspension assembly 10. The stem 12 may terminate at its upper end in a connector which is attached to and carried along by an overhead conveyor in a well known manner. Likewise, although four quadrant arms have been illustrated and described, it should be understood that a greater or lesser number of arms may be employed, or a different suspending arrangement entirely utilized.

My suspension assembly consists essentially of four hangers 20, 21, 22 and 23. From FIGURES 1, 2 and 3 it will be observed that the configuration 0r outline of each of the hangers is identical, and a description of one will describe each.

Hanger includes an elongated body-section 25 which terminates, at its upper end, in a smooth curve, or upper hook 26. The lower end 27 of the elongated body portion is canted slightly from the portion above it and terminates in a bottom hook indicated generally at 28. The hook 28 resembles roughly a fishhook and is reversely curved as contrasted to the top hook 26.

Hook 28 curves upwardly to a support point 29 and then slants downwardly to form an internal lip or point 30. The distance between the lip 30 and the inner edge V .31 of the lower end of the elongated body section of the Yet another object is to provide a suspension assembly having only two parts of different configuration, each quiring cores or welds or other special equipment during fabrication.

body portion 25 is a rectangle with rounded edges.

hanger is less than the distance between the depression 32 and a corresponding, oppositely located point along edge 31.

As best seen in FIGURE 4, the cross-section of the The same cross-section is provided, so far as practical, throughout the length of the hanger.

A spacer member for maintaining the four hangers in their relative positions of FIGURE 1 is indicated genations to which the hangers are exposed.

orally at 35. The spacer member is generally U-shaped, as best seen in FIGURE 5. The two generally parallel sides 36, 37 and the bight portion 38 are co-planar. The cross-section taken at any point along the spacer would resemble the cross-section shown in FIGURE 4. In this instance the ends of arms 36, 37 have been tapered as at 3?, 40 to conserve material and provide a chute or slideway which helps guide a workpiece into place.

A pair of notches or recesses 41, 42 are formed in the leg 36 of the spacer, and a similar pair of notches 43, 44 are formed in leg 37. From a comparison of hanger 2% in FIGURE 3 with the spacer in FIGURE 5, it will be noted that the distance between the inside edge 31 and tip 39 of the lower hanger hook is shorter than the distance between the bottom 45 of a notch and outside edge 46 of the spacer. At the same time the distance between the base 32 and the inner edge 31 of the hanger is greater than the distance between base 45 and edge 46 of the spacer.

The use and operation of my invention is as follows:

My suspension assembly is easily assembled by slipping each of the four hangers into a corresponding notch of the spacer member by bringing the two members together at an angle until the notch and cutaway area beneath lip 30 overlap one another, and rotating one of the parts with respect to another until the plane of the spacer is parallel to the bottom surface 48 of the corresponding hanger. Once assembled the four hangers and spacer may be dropped in place between collar 17 and flange ring 18. The end plate and flange ring allow only a relatively small amount of movement of the hangers along the supporting arm 13, as best seen in FIGURE 2.

Once assembled, the support points 29, 49, 50 and 51 will be disposed in very close to a common plane. The plane of support is indicated roughly at 52 in FIGURE 2. The workpiece which is to be heat treated, is slipped into the opening'formed between the downwardly diverging hangers and placed upon the 4-points of support. Although 4 points of support are shown, it is quite probable that only three points are operative at any instant, due to the very small dimensional variation which results, firstly, from casting tolerances, and secondly, from dimensional changes resulting from the temperature vari- It is entirely possible that if expansion and contraction occurs at differing rates, different support points may be effective at different times during a trip through a heat treating furnace. V e

As best seen from FIGURES 1 and 2, all parts are flat and may therefore be easily cast, either by the, shell molding process or in a conventional green sand mold. There are no sharp corners, as best seen in FIGURES 3, 4 and 5, and therefore there are no areas in which stress concentration, and eventually rupture, will occur.

When assembled, no part is rigidly connected to an adjacent part. The spacer merely rests on the four bottom surfaces formed in the four lower hooks of the hangers, and since ample clearance is provided the parts are free to expand and contract without transmitting any expansion or contraction stresses to an adjacent part.

In addition, the weight of the work to beheat treated is distributed among three, and often four, separate hanger members which correspondingly reduces the additional stress derived from the Weight of the workpiece on any one part as contrasted to the conventional cage type construction; This makes possible the use of thinner sections which is anadvantage since the magnitude of stresses resulting from temperature variation is considerably less than those, present in a single piece of equal tensile,

strength. i V

The form is very simple and ideally suited for sand casting. No cores are necessary and the patterns are relatively simple and easyto make. V

Should, any individual hanger crack during travel through a heat treating furnace, the remaining three hang l ers will assume the loadand the workpiece will be safely conveyed the length of the furnace. If one of the parts cracked in prior construction, the crankshaft or work piece carried thereby dropped to the bottom of the furnace and was lost.

A substitute hanger, and even a substitute spacer, may be quickly added to the remainder of the assembly without removing the assembly from the spider 11 before another workpiece is supported on it.

In addition, only two basic parts are used in my assembly which reduces inventory problems to a minimum. Further, should one part break, the entire assembly need not be thrown away because of the interchangeability of the parts.

Various materials may be used for the hangers and spacers. As a rule, the material used will depend to a considerable extent upon the service to which it is to be subjected. For assemblies intended for use in heat treatment furnaces high nickel, high chromium ferrous alloy may be employed. One acceptable material consists of 35 percent nickel, 15 percent chrome and the balance iron with the usual impurities.

Although a preferred embodiment of the invention has been illustrated and described it will at once be apparent to those skilled in the art upon reading the above description that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, it is my intention that the invention be limited, not by the foregoing description, but only by the scope of the appended claims when read in conjunction with the pertinent prior art.

I claim:

1. A. suspension assembly for supporting heavy objects which are to be exposed to elevated temperatures in a treatment zone, said suspension assembly including, in combination, 7 a V at least three suspending members, each suspending member having means, at its upper end, for connecting it to a base structure which enables each suspension member to be movable independently of one another and of the base structure due to dimensional changes resulting from differences in temperatures to which the suspension members are exposed, a bodily rigid smoothly contoured spacer member and means for loosely connecting the spacer member to the suspending members,

said spacer member maintaining the lower end portions of the suspending members at fixed distances from one another within the limits of the loose-connections therebetween,

said spacer member and suspending members, when loosely connected to one another, providing at least a three point support in a common plane for a workpiece, the points of connection of the suspending members to the spacer member being substantially coextensive with the maximum width dimension of the spacer member to thereby provide maximum accessibility for receiving the heavyobjects to be supported.

2. The suspension assembly of claim 1 further characterized in that the configurations ,of the suspending members are substantially identical one with the other, each member having a'substantially constant cross-sectional area throughout. 7 a

3, The suspension assembly of claim}, further characterized in that the spacer member is substantially symacterized in that the bodily rigid spacer member is loosely connected to the lower portions of the supporting members. a

5. A'suspension assembly for supporting objects to be exposed to an elevated temperature environment, said suspension assembly including, in combination,

at least two pairs of hangers, each hanger having means, at its upper end, for connecting it to a base structure which enables each hanger to be movable independently of one another and of the base structure due to dimensional changes resulting from dilierences in temperature to which the hangers are exposed, a bodily rigid, generally U-shaped spacer and means for loosely connecting the spacer to the hangers,

said spacer maintaining the lower ends of opposite pairs of hangers fixed distances from one another within the limits of the loose connections between the hangers and the spacer,

said pairs of hangers being located generally opposite one another along the two generally parallel arms of the generally U-shaped spacer to thereby provide an opening in which the workpiece to be supported may be placed,

said spacer and any three of any four hangers, when loosely connected to one another, providing at least a three point support for a workpiece in a common, generally horizontal plane.

6. The suspension assembly of claim 5 further characterized in that each of the hangers has a substantially uniform cross-sectional area along its length, and the spacer similarly has a substantially similar cross-sectional area from end to end.

7. The suspension assembly of claim 5 further characterized in that the upper ends of each of the hangers is formed in the shape of a hook whereby the hangers may be suspended from a generally horizontally oriented support base received within the hook.

8. The suspension assembly of claim 5 further characterized in that the lower portion of each hanger terminates in a hook, the uppermost point of each hook being a point of support for a workpiece,

the spacer having a plurality of slots extending generally perpendicularly to the long dimension of each arm, each slot being of a width sufiicient to loosely receive an assocaited hanger.

9. The suspension assembly of claim 8 further characterized in that the clearance between the inside of the hook and the adjacent portion of the hanger which lies in a generally vertical plane is less than the width dimension of the spacer member, but greater than the width of the neck of the slot.

10. A suspension assembly for supporting a workpiece for travel through a heat treating zone, said suspension assembly including, in combination,

four hanger members,

each hanger member terminating, at its upper end, in a hook and having an elongated body portion extending downwardly from the upper end and terminating, at its lower end, in 'a reverse hook,

the uppermost point of each lower hook providing a point of support for a workpiece,

the cross-sectional areas of each hanger member being substantially uniform and substantially identical throughout their length,

and a bodily rigid spacer member for maintaining the hanger members at relatively fixed distances from one another,

said spacer member comprising a generally U-shaped member having two pairs of generally oppositely located notches, each pair of notches being located in one of the elongated arms of the spacer member, said slots being cooperable with the reverse curve hooks at the lower end of the hanger members to loosely connect the spacer member to the hanger members, the cross-sectional area of each spacer member being substantially uniform over a substantial portion of its length, the reverse hooks on the lower end of the hanger members and the slots on the spacer member being so arranged that, when assembled, the points of support formed by the hanger members are substantially co-planar,

said spacer member maintaining the lower end of the hanger members a sufficient distance apart to permit the insertion and removal of a workpiece into the spacer member so as to rest on the points of support of the reverse books.

11. A method of assembling a non-rigid suspension assembly of the type having a generally U-shaped bearing member which has a plurality of slots formed in the interior edge of each of the generally parallel legs of the bearing member, each of said slots forming, with the exterior edge of the leg in which it is formed, a relatively narrow neck of solid material, and a hanger member for each of at least two of the slots in each leg of the bearing member, each hanger member having, at its lower end, a hook with a clearance between the hook and shank portion of the hanger member of a lesser length than the neck of its associated slot, the width of the hook opening being greater than the thickness of the neck of the slots, said method including the steps of maintaining the bearing member in a substantially horizontal position,

loosely connecting a hanger member to each of at least two slots on each leg of the bearing member by lining up the hook opening of a hanger member with an associated notch in the bearing member while the hanger member is rotated a substantial angle away from its final, assembled position,

sliding the hook into the slot a distance sufiicient for the neck to clear the hook while the hanger member and bearing member are maintained at a substantial angle to one another,

' rotating the hanger member and bearing member with respect to one another when the neck clears the hook,

repeating the preceding steps until at least two hanger members have been loosely connected to each side of the bearing member, and

connecting the assembled hanger members to an elevated support location.

12. A suspension assembly for supporting objects which are to be exposed to elevated temperatures in a treatment zone, said suspension assembly, including, in combination,

at least three suspending members, each suspending member having means, at its upper end, for connecting it to a base structure which enables each suspension member to be movable independently of one another and of the base structure due to dimensional changes resulting from differences in temperatures to which the suspension members are exposed,

a bodily rigid spacer member and means for loosely connecting the spacer member to the suspending members,

said spacer member maintaining the lower ends of the suspending members at fixed distances from one another within the limits of the loose connections therebetween,

said spacer and suspending members, when loosely connected to one another, providing at least a three point support in a common plane for a workpiece,

the three point supports being formed by the suspending members.

13. A suspension assembly for. supporting objects which are to be exposed to elevated temperatures in a treatment zone, said suspension assembly, including, in combination,

at least three suspending members, each suspending member having means, at its upper end, for connecting it to a base structure which enables each suspension member to be movable independently of one another and of the base structure due to dimensional changes resulting from diiferences in temperao 7 tures to which the suspension members are exposed, a bodily rigid spacer member and means for loosely connecting the spacer member to the suspending members, said spacer member maintaining the lower ends of the suspending members at fixed distances from one another within the limits of the loose connections therebetween,

loosely connected toone another, providing at least a three point support in a common plane for a workpiece,

the bodily rigid spacer member being loosely connected to the lower portion of each suspending member, and

I said spacer member and suspending members, when the three points of support being formed on the suspending member.

References Cited by the Examiner UNITED STATES PATENTS CLAUDE A. LE ROY, Primary Examiner. 

1. A SUSPENSION ASSEMBLY FOR SUPPORTING HEAVY OBJECTS WHICH ARE TO BE EXPOSED TO ELEVATED TEMPERATURES IN A TREATMENT ZONE, SAID SUSPENSION ASSEMBLY INCLUDING IN COMBINATION, AT LEAST THREE SUSPENDING MEMBERS, EACH SUSPENDING MEMBER HAVING MEANS, AT ITS UPPER END, FOR CONNECTING IT TO A BASE STRUCTURE WHICH ENABLES EACH SUSPENSION MEMBER TO BE MOVABLE INDEPENDENTLY OF ONE ANOTHER AND OF THE BASE STRUCTURE DUE TO DIMENSIONAL CHANGES RESULTING FROM DIFFERENCES IN TEMPERATURES TO WHICH THE SUSPENSION MEMBERS ARE EXPOSED, A BODILY RIGID SMOOTHLY CONTOURED SPACER MEMBER AND MEANS FOR LOOSELY CONNECTING THE SPACER MEMBER TO THE SUSPENDING MEMBERS, SAID SPACER MEMBER MAINTAINING THE LOWER END PORTIONS OF THE SUSPENDING MEMBERS AT FIXED DISTANCES FROM ONE ANOTHER WITHIN THE LIMITS OF THE LOOSE CONNECTIONS THEREBETWEEN, 